Wastewater, particularly industrial wastewater, can be difficult to cost-effectively treat because of its physical and chemical properties. Wastewater can be comprised of various chemical and biological species, including suspended solids. As such, there has been a long-felt but unmet need to more efficiently treat wastewater, particularly industrial wastewater.
The use of dyes as tracing chemicals was patented by John Hoots of Nalco Company in 1988 (U.S. Pat. No. 4,783,314), and subsequent patent applications were filed for specific industrial applications, such as disulfonated anthracenes as inert tracer for boiler water (U.S. Pat. No. 7,220,382).
The synthesis of rhodamine dyes is described in U.S. Pat. No. 4,647,675. As a commercially available dye, Rhodamine WT has been used in hydrological studies of surface water, ground water, and wastewater (Dyes As Hydrological Tracers, by Mon, J. and Flury M, Water Encyclopedia, 95-102; YSI Environmental 1006 E46-01) (2005); and Herbicide tracing in surface water and ground water (YSI Environmental 1006 E46-01).
Industrial wastewater treatment processes have not been able to use fluorescent tracers due to its high fluorescence background and high interfering light-scattering signal from suspended solids. It is very difficult to find an inert dye that overcomes the interference from high fluorescent background and high suspended solids present in industrial wastewater. The interference from charged coagulants and flocculants and other contaminants in wastewater add difficulty in finding a suitable inert fluorescent dye.
Accordingly, there is a need for and clear utility in a fluorescent dye that can be used in tracing treatment chemicals in industrial wastewater. Desirably, the dye will overcome the obstacles presented by industrial wastewater that make it difficult to fluorescently trace treatment chemicals.
The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 CFR § 1.56(a) exists.